Several arenaviruses, chiefly Lassa virus (LASV), cause hemorrhagic fever disease in humans and pose a great public health concern in their endemic regions. Moreover, evidence indicates that the worldwide-distributed prototypic arenavirus lymphocytic choliomeningitis virus (LCMV) is a neglected human pathogen of clinical significance. What are needed are live attenuated arenavirus vaccines comprising recombinant arenaviruses that 1) grow well in cultured cells, 2) do not exhibit virulence in vivo, and 3) provide protection against a lethal challenge with wild type virus.